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迪杰斯特拉算法(图文)

第十三双眼睛2023-10-23【数据结构与算法】人已围观

简介迪杰斯特拉算法

迪杰斯特拉算法

package com.xingchen.day017;
import java.util.Arrays;
public class Dijstra {
public static void main(String[] args) {
char[] vertex = {'A','B','C','D','E','F','G'};
int[][] matrix = new int[vertex.length][vertex.length];
final int N = 65535;
matrix[0] = new int[]{N,5,7,N,N,N,2};
matrix[1] = new int[]{5,N,N,7,N,N,3};
matrix[2] = new int[]{7,N,N,N,8,N,N};
matrix[3] = new int[]{N,9,N,N,N,4,N};
matrix[4] = new int[]{N,N,8,N,N,5,4};
matrix[5] = new int[]{N,N,N,4,5,N,6};
matrix[6] = new int[]{2,3,N,N,4,6,N};
Graph graph = new Graph(vertex, matrix);
graph.showGraph();
graph.dsj(6);
graph.show();
}
}
class Graph {
char[] vertex;//顶点数组
int[][] matrix;//临接矩阵
VisitedVertex vv;
public Graph(char[] vertex,int[][] matrix) {
this.vertex = vertex;
this.matrix = matrix;
}
public void showGraph() {
for (int[] link: matrix) {
System.out.println(Arrays.toString(link));
}
}
//index表示出发顶点对应的下标
public void dsj(int index) {
vv = new VisitedVertex(vertex.length, index);
//更新index顶点到周围顶点的距离和前驱顶点
update(index);

for (int j = 1;j<vertex.length; j++) {
//选择并返回新的访问顶点
index = vv.updateArr();
update(index);
}
}
private void update(int index) {
int len = 0;
for (int j = 0;j<matrix[index].length;j++) {
len = vv.getDis(index) +matrix[index][j];
if (!vv.in(j) && len < vv.getDis(j)) {
vv.updatePre(j,index);
vv.updateDis(j,len);
}
}
}
public void show() {
vv.show();
}
}
class VisitedVertex {
private int[] already_arr;
private int[] pre_visited;
private int[] dis;

public VisitedVertex(int length,int index) {
this.already_arr = new int[length];
this.pre_visited = new int[length];
this.dis = new int[length];
Arrays.fill(dis, 65535);
already_arr[index] = 1;//设置出发顶点已被访问
this.dis[index] = 0;
}
//判断index对应的顶点是否被访问过,如果访问过，就返回true,否则返回false
public boolean in(int index) {
return already_arr[index] == 1;
}
//更新出发顶点到index的距离
public void updateDis(int index, int len) {
dis[index] = len;
}
//更新节点的前驱节点为index节点
public void updatePre(int pre, int index) {
pre_visited[pre] = index;
}
//返回出发顶点到index的距离
public int getDis(int index) {
return dis[index];
}
public int updateArr() {
int min = 65535,index = 0;
for (int i = 0;i<already_arr.length;i++) {
if (already_arr[i] == 0 && dis[i] < min) {
min = dis[i];
index = i;
}
}
already_arr[index] = 1;
return index;
}
public void show() {
System.out.println("========");
System.out.println(Arrays.toString(already_arr));
System.out.println(Arrays.toString(pre_visited));
System.out.println(Arrays.toString(dis));
char[] vertex = {'A','B','C','D','E','F','G'};
int count = 0;
for (int i: dis) {
if (i != 65535) {
System.out.print(vertex[count] + "("+i+")");
} else {
System.out.println("N");
}
count ++;
}
System.out.println();
}
}

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